Standing wave heat engine with means for supplying auxiliary air



March 6, 1951 A. G. BODINE, JR 2,543,753

STANDING WAVE HEAT ENGINE WITH MEANS FOR SUPPLYING AUXILIARY AIR Filed June 13, 1947 3 Sheets-Sheet l [/7 venfor" March 6, 1951' A. G. BODINE, JR

STANDING WAVE HEAT ENGINE WITH MEANS FOR SUPPLYING AUXILIARY AIR 3 Sheets-Sheet 2 Filed June 15, 1947 3 l 7 n i W p I.

[n vent ar 55/ ?.$0dmgin,

Alla/neg March 6, 1951 A 6.500: JR 2,543,758

. E, STANDING WAVE HEAT ENGINE WITH MEANS FOR SUPPLYING AUXILIARY AIR Filed June 13, 1947 I5 Sheets-Sheet 3 Compressor I56 lwpalm iizrbine uel 1 I53 75 r45 1 m t 3/5.?

Patented Mar. 6, 1951 UNITED STATES PATENT OFFICE STANDING WAVE HEAT ENGINE WITH MEANS FOR SUPPLYING AUXILIARY AIR Albert G. Bodine, Jr., Van Nuys, Calif.

Application June 13, 1947, Serial No. 754,559

(Cl. Gil-85.6)

17 Claims. I

This invention relates generally to combustion apparatus, and more particularly to thermal jet engines of the acoustic standing wave type, as is disclosed in my copending patent application Serial No. 439,926, filed April 21, 1942 -(now abandoned), entitled Method and Apparatus for Generating a Controlled Thrust, and of which the present application is a continuation-inpart. See also my Patent No. 2,480,626, issued August 30, 1949. Engines of this type have such diverse applications as jet propulsion wherein their thrust producing characteristics are of primary importance, and as blowers or compressors utilized, for example, to supply heated air under pressure to a gas turbine, or to supply a large volume of warmed air for space heating.

In its gas turbine application, used between the usual compressor and the turbine, the present invention serves several advantageous purposes, including increase in the expansion ratio of the turbine, reduction of the temperature of the heated gases to values which the turbine blades can withstand, and as a topping unit, designed to extract heat energy from the combustion heated gases and convert it into mechanical or kinetic energy of gas flow through the system.

In accordance with the present invention, there is utilized, in most applications, a resonated tubing or cavity having a closed end and an open end, the former being the location of a pressure anti-node, and the latter being the location of a velocity anti-node. In the special case of a straight tubing closed at one end and open at the other, its length will be substantially one-quarter the length of the wave corresponding to its resonant frequency. Thermal drive means in the form of means for intermittent fuel combustion at a resonant frequency of the tubing is provided and either discharges to or is located at the pressure anti-node. Primary air necessary for the initial combustion is supplied, sometimes under pressure, to the combustion region.

In such an engine, each com-bustion launches a wave of compression traveling with the speed of sound down the column of fluid within the resonant tubing. By reason of alternate inverse and like-kind reflection at the open and closed ends of the tubing, a negative pressure peak is created at the combustion zone one-half cycle following each explosion, and a positive pressure peak is created at said zone a full cycle followmg each explosion. Assuming the fuel supply and ignition means to betimed to set of! an explosion once each cycle, this positive pressure peak appearing once each cycle at the combustion zone coincides with and reinforces the periodic explosion.- In some embodiments, it also compresses the fuel charge prior to combustion, and the described negative pressure wave may be utilized to draw fuel and/ or air into the combustion zone.

By the means described in the preceding paragraph, a standing wave is established in the tubing with the aforesaid pressure anti-node at the combustion zone and velocity anti-node at the open end. In result, there is a "direct current flow of combustion gases down the tubin to discharge from its open end, upon which is imposed an "altemating curren flow due to the standing wave. At the pressure anti-node region, this alternating current" flow is, of course, substantially zero; but at the velocity anti-node, the to-and-fro or alternating current component may be very substantial, usually much greater than the direct current component. The alternating current component results in air being sucked into the open or velocity antinode end of the tubing from virtually all directions during the half-cycle of inward flow (up the tubing), which air flow supplies secondary air to complete combustion and any excess or auxiliary air is jetted straight rearwardly from the tubing along with products of combustion during the half-cycles of outward flow (down the tubing). Depending upon the particular application in hand, this air so taken in at the velocity anti-node region of the apparatus can, if supplied in the proper way and in sufficient quantity, serve several very beneficial purposes, as will appear hereinafter.

It can be seen that the present invention is most conveniently practiced by using the class of resonant cavity having an open end. It is possible however to use other shapes of acoustic resonators provided there is or can be access for fluid introduction to their velocity anti-node regions.

With this introduction it may now be stated that a general object of the invention is to provide a thermal jet engine of the class described having provision for supplying or augmenting a flow of auxiliary fluid, usually secondary air, to the velocity anti-node region thereof.

It is believed that the various beneficial functions fulfilled by the invention can best be set forth in connection with the disclosure of various illustrative types of apparatus incorporating the invention. Reference for this purpose is made to the accompanying drawings in which:

Figure 1 is a longitudinal sectional view of one illustrative embodiment of the invention;

Figure 2 is a view similar to Figure 1 showing a modification;

Figure 3 is a view similar to Figure 1 showing a still further modification;

Figure 4 is a longitudinal sectional view showing an adaptation of the invention to such industrial use as space heating;

Figure 5 is an elevational view, partly in longitudinal section, showing a compressor-turbine combination embodying the present invention;

Figure 6 is a side elevation, partly broken away, showing a modified compressor-turbine combination embodying the present invention;

Figure '7 is a detail view showing an end elevation of a resonant conduit of the embodiment of Figure 6;

Figure 8 shows a modification of Figure 7;

Figure 9 shows a modification of the embodiment of Figure 3;

Figure 10 is a fragmentary longitudinal sectional view of a resonant conduit with a thrust augmenter mounted thereon; and

Figure 11 is a longitudinal sectional view of a jet propulsion apparatus in accordance with the invention.

In Figure 1 is shown an exempliflcation of what I may refer to as an enclosed system, namely, one in which the resonant tubing has its open end discharging into an enlarged housing, or "capacitance chamber." The system of Figure 1 may be used for propulsion, or, by mounting it on a stationary foundation, it may become a blower or compressor, useful for many purposes, and shown in this instance as driving a. gas turbine, whose power may be utilized in any way desired. The turbine might, for instance, be used to drive a conventional supercharger (not illustrated) which furnishes the explosive mixture to the combustion chamber.

Numeral l0 in Figure 1 designates the housing of the enclosed sonic system in its entirety, made up of resonant tubing ll whose flared open and I 2 discharges gases into enlarged chamber i3 and also functions as a sonic wave expander. The tubing H, which has a closed end or head l4, defines a sonic fluid column 15. Pressure pulses from a combustion chamber 16 of an internal combustion engine I! are applied directly to the fluid column by two illustrative means which may be used alternatively or together. The first comprises an exhaust passage l8 conducting the exhaust gases from the combustion It to the fluid column i5, and the second comprises an auxiliary exhaust passage 20 conducting a portion of the exhaust gases to the fluid column. The flow of exhaust gases through the former is controlled by a conventional exhaust valve 2| operated by an engine driven cam 22, and the latter includes an adjustable spring-loaded valve 23, the compression of which is adjustable by turning a screw 24. Admission of a fuel-air mixture to the combustion chamber is by way of a conventional intake valve operated by an engine driven cam 26, the fuel being ignited by a spark plug 21. It will be clear that this intake and explosion system will be modified in the case of Diesel or injection type engines in accordance with known practice.

The enlarged housing or capacitive chamber I3 is provided, in this instance, with two outlets and 3], the former of which leads straight rearwardly from chamber i3, that is, axially with respect to tubing ii, and the latter of which is here shown as discharging laterally from chamber [3. While not in all cases necessary, these outlets 30 and 3i are here shown as provided with spring-loaded valves 32 and 33, respectively, which are adapted to hold a certain back pressure within the system. Outlet 30 may discharge exhaust gases in a rearwardly direction for jet propulsion purposes, or may be coupled to any conduit or system requiring a supply of heated gases under pressure. Outlet 3| is shown as coupled into a gas turbine 34, which is shown as arranged to drive a shaft 35 transmitting power available for any useful purpose, such as driving the engine supercharger, etc.

The operation of the system results in the establishment of a velocity anti-node V at the open end l2 of the tubing Ii, and a pressure anti-node P at the closed end thereof. The present invention provides a conduit means arranged for introducing additional fluid, preferably and usually air, to the velocity anti-node region V of tubing i i. In Figure 1, this means comprises the air pipe 31, fed by any suitable source of supply, and controlled by a poppet valve 38, which is in turn operated by an engine driven cam 39. It is to be understood that the timing of cam 39 is such that valve 38 will be opened for introduction of fluid to zone V during the half-cycle of operation wherein fluid in the velocity antinode region V is in motion up to the tubing II, that is, toward the left in Figure 1.

The system of Figure 1 may be operated on several cycles, but the following typical cycle will be sufilciently illustrative for present purposes. It will be assumed, first that only the exhaust passage is is to be used, the alternate passage 20 being either omitted, or valve 23 held closed. During the expansion stroke of engine II .(which may be assumed to be a four cycle engine), the valve 2| opens to permit discharge of exhaust gases to the head end of tubing ii, thus delivering a pressure pulse to the head end of the fluid column IS. A wave of compression travelling with the speed of sound is hence launched down the fluid column, to be discharged or expanded into the enlarged capacitance chamber l3. Because of the expansion, the open end of the tubing ll reflects the wave as a wave of rarefaction travelling back up the tubing, and

creating a negative pressure peak at the head end M of the tubing at the instant of its arrival. This wave of rarefaction is in turn refiected by the head end Id of the tubing as a wave of rarefaction trave ling back along the tubing toward the open end i2 thereof. An inverse reflection again occurs at open end l2, so that a wave of compression now travels back up the tubing, to create a positive pressure peak at the instant of its arrival at head l4, all in accordance with well known quarter-wave pipe theory. If the engine I! is so timed as to deliver another exhaust pulse in the pipe [8 at this same instant, i. e., each time a positive pressure pulse returns at substantially maximum amplitude to head M by travelling along the tubing II, a reinforced pressure peak will be created at the head end M of the tubing, and the system will operate at resonance, with a pressure antinode established at P, and a velocity antinode established at V. According to this illustration, the four cycle engine I! will be operated at a speed to assure delivery of exhaust pulses at the fundamental resonant frequency of the tubing II, The tubing might also be resonated, however; by operating the engine at either a multiple, or a sub-mintiple of the fundamental frequency. Moreover the engine |1 might equally well be a two cycle engine, it making no difference insofar as the present invention is concerned by what specific means the pressure pulses are delivered to the tubing so long as they arrive at a resonant frequency of the tubing. If it is desired to make use of the second exhaust passage 20, the corresponding valve 23 may be timed to open before, after, or with the valve 2|. The use of this valve 23, with its timing differing from that of valve 2|, is more particularly described in my aforementioned application Serial No. 439,926.

Attention should be called to the fact that the described standing wave established in the tubing assists in theperformance of the cycle events of engine l1. Thus, the negative pressure halfcycle at zone P may partially overlap the scavenging stroke of engine l1, and thus aid in scavenging. Since the negative pressure half-cycle will overlap the intake stroke of the engine, again, by merely timing the exhaust valve 2| to remain open on into the intake stroke, this negative pressure, may be utilized to assist in drawing the fuel charge into the combustion chamber, and may even be utilized to open the valve 25, the cam 26 being assumed to be omitted. Finally, if the exhaust valve 2| remains open on into the compression stroke of engine IT (or is omitted entirely). the rising positive pressure at zone P may assist initially in compressing the fuel charge within chamber Hi.

It will be seen that exhaust gases are thus intermittently introduced to the tubing II, and these will travel down the tubing, at a velocity which is, of course, much lower than the previously mentioned waves of compression and rarefaction, to be introduced into housing l3, and finally discharged via either or both of outlets 30 and 3|. Thus, there is what may be described as a direct current flow of gases down the tubing During alternate half-cycles of the standing wave in tubing II, when the direction of flow is up the tubing, or to the left as viewed in Figure 1, fluid is drawn into the tubing through its open end I! from the housing l3, and during the remaining half-cycles this fluid is discharged from open end |2 back into housing |3. so that an alternating current flow of gases is superimposed on the previously described direct current gas flow. During the first mentioned half-cycles (flow toward the left), the valve 38 i is opened by cam 39 and auxiliary fluid, preferably air, introduced by way of conduit 31. This introduced air may, of course, be introduced under pressure, but the virtue of the arrangement is that the velocity of gas flow within the tubing creates a suction which draws or pumps the auxiliary air into and up the tubing The air so introduced via conduit 31 has a number of beneficial functions in the system of Figure 1. It acts first as a flame holder within the tubing I. It should be explained that in the absence of the provisions of the present invention, flame from the combustion chamber may extend throughout the length of the tubing H,

and may even be projected through the outlets from the chamber l3. The air introduced via the conduit 31 rams the flame back up the tubing toward the closed head end thereof, and also furnishes sufllcient additional oxygen to clean up and complete the combustion within a reasonably 6 short distance from the head end region of the tubing. The tail end region of tubing II, and the chamber l3, hence run at a cooler temperature, and the possibility of flame reaching the turbine 34 is avoided.

The air introduction by way of conduit 31 to the velocity anti-node region V, where substantial gas velocities are experienced, also creates a desirable turbulence which results in intimate mixing of the introduced oxygen with any remaining unburnt fuel, thereby further assuring completion of combustion.

It should be noted that by virtue of the velocity fluctuations at the region V resulting from the standing wave established in the tubing, a pumping effect is exerted upon the air introduced via the conduit 31. Thus, the system functions as an acoustic pump, energy from the combustion flame being successively transformed into acoustic wave energy, and thence into kinetic energy of flowing gas. An increased volumetric gas flow results, at reduced temperature, as is desirable for many purposes, including space heating. There are also advantages with particular reference to the turbine 34 fed by way of the outlet 3|, but these can best be left for discussion in connection with later described specific turbine adaptations (Figures 6 and 7).

In the embodiment of Figure 2, the resonant tubing has a flared open end 4|, and has at its opposite end a head or closure 42, adjacent which is the combustion chamber region 58 of the system. A fuel intake passage 43 opens through this head 42, and is controlled by a suitable poppet valve 45 operated by cam 45 on cam shaft 41'. The latter may be driven by any speedgoverned drive means, such an electric motor, internal combustion engine, turbine, etc. Coupled to intake passage 43 is a supply pipe 48 to which the mixture is fed from a supercharger 49, the mixture being formed by a suitable carburetor 5|). Cam shaft 41 may also drive the supercharger 49, as well as a magneto 5|. As an alternative or supplementary fuel supply means, there may be provided a supplementary fuel injector pump 52 driven from cam 53 on cam shaft 41 and acting to meter a liquid fuel directly into the combustion chamber 58 via injector nozzle 59. The magneto 5| and cams on shaft 41 are, of course, arranged to provide the desired timing of fuel introduction and ignition (as by use of spark plug 54 connected to magneto 5|).

Tubing 40 opens at its end 4| into enlarged housing or capacitance chamber 56, having discharge outlet 51, which in this instance is shown as valveless, and as directed straight rearwardly for jet propulsion purposes. The outlet 51 may, of course, be coupled to any conduit, accumulator, turbine, etc., and the apparatus in any such instance may be stationarily mounted.

Head 42 is shown provided with a second fluid passage 60, controlled by an inwardly opening spring-closed poppet valve 6|, which is capable of opening automatically upon occurrence of a predetermined sub-atmospheric pressure within the head end or combustion region of tubing 4|). The valve-controlled fluid passage 60 is connected by pipe 62, a capacitance chamber 63 and another pipe 64, with the capacitance chamber 56, the capacitance chamber 63 being used to render the interconnection between the chamber 56 and the combustion region non-resonating, i. e., nonsonic, at the operating frequency of the remainder of the apparatus, so as to prevent interference. The capacitance chamber 63 is provided with an air intake means, here shown in the form of a forwardly facing scoop 65, controlled by spring-loaded automatically opening intake valve 66. adapted to open upon predetermined suction within chamber 63 or upon pre-determined ram pressure in scoop 65. The system 62, 63 and 64 can be utilized to return gases from chamber 55 to combustion zone 56 in order to reduce negative pressure peaks in the latter on alternate half cycles, and the valve controlled scoop 65 permits additional air introduction, all as explained in my aforesaid prior application Serial No. 439,926.

On the other hand, by either blocking valve 6| closed, using such a stiff spring that it will not open under negative pressure peaks in the combustion space 58 (or with the possible exception of only momentary opening at extreme negative peaks) or by eliminating the valve 6| and pipe 62 entirely, the scoop 65, chamber 63 and pipe 64 may be utilized to introduce secondary air to chamber 56 and thence to the velocity anti-node region V of tubing 40. For this purpose, the spring for valve 66 should be quite soft or light, so that the valve opens readily under the ram pressure that will exist within the scoop. The function of the valve in this case is simply to guard against any possibility of back flow. The opening of pipe 64 into chamber 56 is made near the tubing opening 4| so that the introduced air may be drawn into the opening 4| before it has the opportunity to be seriously diluted with the exhaust gases within chamber 56.

Operation of the system of Figure 2 is in general similar to that of Figure 1, with, however, certain differences owing to the location of the combustion chamber in the resonant tubing, and the elimination of the piston, as well as the valves between the combustion chamber and the gas column in the resonant tubing. Fuel introduced to the combustion chamber 58 is periodically exploded by a properly timed spark at plug 54, or by lingering flame from previous explosions, and positive pressure pulses (waves of condensation) are thereby launched down the tubing. These pressure pulses behave exactly as in Figure 1, each being reflected at open end 4| as a traveling negative pulse, which creates a negative pressure peak at combustion zone 58, and by reflection by the head 42, then travels back to open end 4|, where it is reflected as a positive pulse traveling back to head 42. The latter creates a positive pressure peak at the combustion zone, and the engine is so timed with relation to the length of tubing 40 that an explosion occurs simultaneously with the attainment of this positive pressure peak. Accordingly, the gas column in the tubing is resonated, and a standing wave is created, with a pressure antinode P at the closed head end of the tubing 40 and a velocity anti-node at the open end 4| thereof. The intake valve 45 is timed to open during the negative half-cycle at the zone P. During this negative pressure condition at P the pressure thereat will be less than the pressure developed by the supercharger, so that a combustible mixture will enter the zone P past the valve 45. Thereafter, the pressure in zone P builds up to positive peak value due to the resonance and standing wave pattern in the fluid column. As this pressure builds up, it compresses the fuel charge, and the ignition system functions to ignite the charge near the instant of maximum pressure to increase further the amplitude of the positive pressure pulse resulting at P from the standing wave. As already mentioned, according to one mode of operation, the valve 6| may open during the negative pressure half-cycle to admit additional air and/or gases returned from the chamber 56. On the other hand, in accordance with the principles of the present invention, the valve 6| may be substantially or entirely blocked, the spring loading of valve 66 made relatively light, and the air intake means 65 and pipe 64 utilized to furnish additional air to chamber 56 at a point therein such that said air may be periodically drawn into the velocity anti-node region V via open end 4| of tubing 46 and thus serve the same purpose as the air taken in through the conduit 31 in Figure 1.

Thus, excepting for the method of creating the pressure pulses at the head end of the sonic column within tubing 40, the system operates similarly to that of Figure 1. The capacitance chamber 56 will be noted to have a valveless discharge opening 51 directed straight rearwardly, such as may be used most effectively for jet propulsion purposes. On the other hand, outlets and uses such as shown and described in connection with Figure 1 are applicable to the system of Figure 2, and contrariwise, the valveless jet discharge outlet 51 of Figure 2 might be employed in the system of Figure 1.

Figure 3 shows a modification of Figure 2, and corresponding parts will accordingly be identified by corresponding reference characters, but with the suffix a used in each instance in the case of Figure 3. In Figure 3, the capacitance chamber 56a is shown as provided with a rearwardly directed jet discharge outlet 10, provided with spring-loaded discharge valve 1|, and with lateral outlet 12 coupled to gas turbine 13 which discharges at 14. The turbine 13 drives a shaft 15 which in turn drives compressor or supercharger 16, and the latter is connected by pipe TI to intake passage 43a. A carburetor may be used in connection with compressor 16 and pipe 11, if desired, but the fuel injection nozzle 59a will serve in Figure 3 as an illustrative fuel supply means. In Figure 3 the air intake passage 60a in head 42a connects to an air scoop 80, and the pipe 62 of Figure 2 is eliminated. Air introduction by way of passage 60a is hence made independent of members 63a to 66a, and the adjustment or operation of the spring-loaded valve 6|a has no effect on the function of said members, whose only function is to take in secondary air and feed it to the velocity anti-node region V of tubing 40a.

The embodiment of Figure 3 shows how the turbine 13 may be used to drive the supercharger, and shows also how the members 63a to 66:: may be made entirely independent of the valve 6|a. Additionally, the turbine shaft 15 is indicated as driving a shaft 82 through a gear box 83, the shaft 82 being available for any desired purpose. Aside from these departures, the embodiment of Figure 3 operates in the fashion of Figure 2.

Reference is next directed to Figure 4, showing an adaptation of the invention to such a typical purpose as space heating. A resonant tubing 90, having an open end 9| and a head 92 closing its other end, is annularly spaced inside a large air duct 95, which is here shown as having a somewhat convergent section 96 just beyond the open end 9| of tubing 90. The left hand end of the duct 95 may be supplied with air in any desired manner, not shown, while the right hand end thereof may lead to any desired point of discharge.

The head end 92 of tubing 90 is equipped with a plurality of intake passages 93 controlled by spring-loaded inwardly opening poppet valves 94, adapted to open automatically upon development of a pressure depression inside the head end region of tubing 90. A bell-mouth 97 on the head end of tubing 90 receives air from the flow within duct 95 and directs it to intake passages 93, while a fuel supply pipe 98, which may supply any suitable powdered, liquid or gaseous fuel, discharges inside the'bell mouth 91. A suitable mixture of primary air and combustible fuel is thus formed within the bellmouth 91, to be drawn in through the valve controlled passages 93. The valve springs are preferably tuned to a higher frequency than the resonant frequency of the tubing 90, and may readily be set into oscillation to pass fuel. For

starting purposes, the pressure of the fuel jetted from pipe 98 will unseat the valves sufllciently to introduce a combustible fuel charge into the head end region of the tubing 90. This charge is ignited by spark plug 99 to initiate operation, and the spark plug may be used also during normal operation, but the combustion flame tends to linger in the head end region of the tubing 90 throughout the operating cycle, and will thereafter serve, after a finite ignition delay time interval, to ignite each successive charge admitted past the valves 94. To aid in holding this flame between explosions, an annular inwardly projecting flame holder or shroud I may be placed inside on the inner wall of tubing 90 near the head end thereof. The wave exciting combustion zone then, becomes the space IIII between this shroud I00 and the head 92,

and between explosions, an outside ring of attenuated-velocity flame remains in a position adjacent the wall of tubing 90 and in back of the annulus I00. As already stated, this is enough for subsequent combustion, which will occur when the compression has been raised to its positive peak by the usual standing wave, which as in the other cases has its pressure antinode P at the combustion zone, and its velocity anti-node V at the open end 9|. By constricting the tubing 90, the shroud I00 also serves to shield the intake valves from excessive heat radiation from afterburning down stream in tubing 90. v

The combustion driven resonant tubing of Figure 4 will operate on a cycle which is like that of the tubing 40 of Figure 2, with the exception that fuel is admitted to the combustion zone past valves which open automatically in response to negative pressure at P. The air flow around the outside of tubing 90 in the duct 95 is directed by the deflector IIO, which turns a portion of said flow radially inward immediately to the rear of the open end III of tubing- 90, said air being thus supplied to the velocity anti-node region V of said tubing, and being drawn thereinto on alternate half-cycles (while the direction of velocity is toward the left). as in previously described embodiments. During the remaining half-cycles, this air is discharged from the tubing 90 along with products of combustion, to be carried away by the reduced duct III. The outside air in duct 95 not-thus turned in by deflector II 0 passes through suitable apertures H2 in the supporting wall II3 for the deflector.

The duct air drawn into the tail end portion of tubing. 90 and then expelled therefrom has ing 90, and completion of combustion, as have been already described in connection with the earlier embodiments. It will be appreciated that in addition, this outside duct air so mixed with the products of combustion from tubing 90, and so pumped along the duct by the acoustic pumping action of the standing wave in tubing 90, results in the production of a large mass flow of warmed air, suitable for space heating or similar purposes. Not only will the air sucked entirely into the open end of tubing be heated, but eventually, by heat transferrence along the duct extension III, all the air flowing along the duct will be warmed, including that passing through apertures II2. It should be understood that the air turned inwardly by the deflector H0 and sucked into and then expelled from the end of the tubing 90 will receive kinetic energy from the standing wave in said tubing, and, by aspiration, will transfer a portion of this energy to the surrounding air in the duct so that the overall effect on the total air flow in the duct III at a distance beyond the end of tubing 90 is both an increase in temperature, and an increase in velocity owing to the sonic pumping action of the standing wave. In many instances this sonic-propelling action is sufflcient to cause all air flow required so that air intake to duct may be at atmospheric pressure, with no blower needed.

In Figure 5 is shown a compressor-turbine combination utilizing a form of the present invention for several beneficial purposes. The compressor I20 and gas turbine I2I are axially arranged, the compressor being driven by turbine drive shaft I22, and the units I20 and I2I being axially spaced, as shown. Insofar as the present invention is concerned, the compressor and turbine may be of any suitable design, and typical details need not be disclosed herein. The compressor outlet has coupled toit one end of an air duct I24, the other end of which is coupled to the turbine intake, as indicated. Annularly spaced within duct I24 isa resonant, combustion-driven standing wave tubing I25, having open end I26 facing downstream in the duct, and

into the head end I21 of which is connected a quarter-wave intake pipe I28 having air intake scoop I29 facing upstream in the duct. The quarter-wave intake pipe I28, which takes the place of the intake valves of the other embodiments, is more particularly described in my copending application Serial No. 728,766, filed February 15, 1947, entitled Jet Propulsion Apparatus. Sufllce it to say here that it eliminates the necessity for valves, and supplies air at constant velocity without its presence substantially attenuating the standing wave in the tubing I25. Fuel (liquid, powdered, or gaseous) is introduced by way of fuel supply pipe,l30 entering intake pipe I28, and ignition, 'at least for starting, is by means of spark plug I3I. A baflie I32 is useful to retain the flame between explosions. As set forth in my'aforesaid application Serial No. 728,766, such an apparatus will operate automatically at the resonant frequency of the quarterwave tubing I25, with the establishment of a pressure anti-node P at the combustion zone, a velocity anti-node V at the open end of tubing I25, and a velocity anti-node V at the intake end of pipe I28.

The compressor I20 will be understood to supply air under an elevated pressure to duct I24,

the same advantageous'uses in regard-to hold- 7 wherein it flows around the outside of tubing 11 I25, a portion thereof ending pipe I28 to operate the acoustic bumer Jacket unit I25. Operation of the latter is as usual, with intermittentcombustion occurring at P at the resonant frequency of the quarter-wave tubing I25 so as to maintain the usual standing wave therein. A part of the air flowing along the outside of tubing I25 turns radially inward just beyond the end of the latter to enter its open end on every alternate half-cycle, to be subsequently expelled therefrom on the succeeding l'alf-cycle, as will now be understood without repeating the reasons therefor. This air flow functions in the manner already described to ram and hold the flame back in the head end of the tubing I25, and to complete the combustion.

The temperatures reached in the combustion zone of tubing I25 are excessive for the turbine, and the auxiliary air that enters into the open tail of the tubing I25 aids in reducing the temperature of the gases to a permissible maximum. Because of the effective mixing of this auxiliary air with the products of combustion that results from the turbulent condition created at the velocity anti-node V, less auxiliary air is required for temperature reduction than would otherwise be necessary.

It is also important to recognize that the described acoustic pumpin of air by the resonant combustion chamber I25 extracts additional work from the highly heated gases, thereby achieving a temperature reduction by direct transformation of heat energy into kinetic energy of flowing gases. The net overall result is that gases are supplied at the entrance to the turbine at increased pressure and reduced temperature. If, for example, the resonant combustion chamber I25 is capable of delivering gases at a pressure which is one and one-half times the pressure of the fuel and air supplied to its combustion zone, then the expansion ratio of the turbine may be one and one-half times the compression ratio of the compressor. In a gas turbine-compressor combination having a compressor with a four to one compression ratio, the resonant combustion chamber will serve to produce combustion gases at a pressure six times the intake pressure of the compressor, and the turbine may operate with an expansion ratio of approximately six to one. It may be stated that the assumed one to one and one-half compression ratio of the resonant combustion chamber is rather conservative; experiments'indicate that a ratio of one to two may be easily practical.

It will be recognized that the, resonant combustion chamber functions as a topping unit," in that it derives useful work (gas pumping effect) from the highly heated gases while reducing the temperature of the gases to values that can be permitted within the turbine.

Such a turbine-compressor combination may be utilized in any appropriate power application; numeral I34 in Figure indicates conventionally a power take-off means, which is simply representative of any suitable power take-off.

Figures 6 and 7 show another turbine-compressor combination utilizing a resonant combustion chamber in accordance with the invention. The compressor I40 and gas turbine I are again axially spaced, and provided with a common shaft I42. The compressor has its intake at I43, and there are a plurality of circumferentially spaced ducts I which connect compressor discharge ports I55 with a common turbine intake chamber (not shown) within the turbine I". The turbine is shown as discharging at I". Annularly spaced within each of ducts I is a resonant quarterwave combustion-driven chamber or tubing I50, its open end facing downstream, and its closed end fitted with spark plug III. A quarter-wave length air intake pipe I52 within the duct has an air scoop I52 facing upstream, and this pipe is shown in Figures 6 and 7 as having a tangential inlet to the head end region of the tubing I50. Figure 8 shows a modified intake pipe I52a which enters the tubing I50 radially, or at right angles.

Fuel is introduced into pipe I52 by means of pump I55 driven by shaft I42. Preferably, the intake pipes I52 for the several units I50 are fed by means of a single radial impulse-typ pump I55 driven by shaft I02 and provided with a plurality of discharge outlets connected by fuel lines I58 to the several pipes I52. Pumps of this type, designed to deliver successive charges to their several outlets at intervals timed by the rotation of the drive shaft, are well known, for instance, in Diesel practice, and need not be detailed herein. By using such a pump, a polyphase relationship can be established between the wave patterns in the several burner units I50, so that, if enough such unts are employed, the common intake chamber immediately ahead of the turbine will experience substantially constant pressure.

The operation of unit I50 is just like the corresponding unit I25 of Figure 5, and the description need not be repeated. The system of Figure 6 shows how a plurality of small unim I50 can be used in parallel between a compressor and a gas turbine so as to achieve a substantially constant turbine intake pressure.

It has been explained how, with a quarterwave jet propulsion apparatus having an openended tail through which products of combustion are jetted, air is drawn into and expelled from this open tail in step with reversing gas velocities occurring thereat. With high forward velocities of the apparatus, the quantityof air that can be aspirated into the tail is reduced markedly by the slip-stream effect. Thus the ap paratus tends to become starved for lack of air on which to work, and a serious self-imposed limitation is thereby imposed on forward velocity.

The difllculty mentioned in the previous paragraph is helped by the apparatus of Figure 9 which shows a modification applicable to either of Figures 1 and 2. The resonant tubing 40b (which may have a head end as in either Figure 1 or Figure 2) has its flared open end Mb discharging inside a bowl-like member 85 fitted therearound and having in this instance a wide mouth 86 which discharges to atmosphere in a rearward direction. A plurality of air intake pipes are fitted into member 85, two alternative types of such pipes being shown. The first, indicated at 65b, is just like the pipe 54a of Fig. 3, having capacitance chamber 55!) and air scoop 55a, but the valve controlling the latter has been removed. The other intake pipe 88 has simply a forwardly facing air scoop 89 at its forward end. These pipes 54b and 88 open into member 85 where the air introduced therethrough will be directed to the velocity anti-node region V within the tubing 40!). Additional air so fed to the velocity anti-node region of the resonant tubing by pipes such as 64b and 88 will supply its requirements notwithstanding high forward velocities of the apparatus.

Figure 10 shows a fragmentary rearward portion of a resonant combustion-driven tubing I of an apparatus such as any of those described 13 herein. Assuming a jet propulsion adaptation this tubing may be assumed to be intended for flight through the atmosphere. To augment the required radially inward and then reverse flow of air into the open tail, a thrust augmenter I8I is used on the tail. This thrust augmenter comprises an air directing or conveying means designed to intercept air from the surrounding slip stream and introduce it into the tail of the tubing. As here shown, this air directing means comprises an annulus I82 which is of modifled airfoil Venturi contour in longitudinal section. This annulus surrounds the rearward extremity of tubing I88, and is annulariy spaced therefrom as shown, being mounted on the shell by means of radial supports I88. An annular baille I88a carried by supports I83 divides the annular space between the tubing I88 and annulus I82 into outer and inner regions I84 and I88, respectively. It will be understood that the jet discharge from the tail through annulus I82 creates a suction at the entrance to these two regions I84 and I88. Air thereby drawn into region I84 between annulus I82 and baille I83a is added to and augments the mass of the propulsive jet directly. That air which is drawn into the inner region I88 is directed radially inward by an inwardly curved portion I88 of baflie I83a, to be influenced by the air flow conditions prevailing at the velocity antinode V located at the discharge opening in the tail. Thus, as in the earlier described embodiments, outside air is sucked into the tail during reverse-flow half-cycles, to be jetted out along with products of combustion during the alternate half-cycles. The augmenter thus augments the supply of outside air to the velocity anti-node region V of the apparatus. It will also be evident that such a device as shown in Figure 18 may be used to advantage on the resonant tubings or "bumer jackets" of the types of apparatus shown in Figs. 4, 5, and 6.

As a further measure to the same end, air intake ports I88 are preferably formed in tubing I88 near the rearward end thereof, being covered over by air scoop means I8I adapted to catch boundary layer air and deflect same in through the ports I 88..

Figure 11 shows a jet propulsion apparatus in accordance with the invention utilizing a ramjet around the burner jacket to envelop it is a super-atmosphere and to supply additional air to the open tail of the burner Jacket. Numeral I88 designates generally an elongated streamlined shell, preferably of circular section, having its greatest thickness a little rearward of its midsection, and being slightly convergent toward its open tail end I 8|, and somewhat more convergent toward its open forward end or nose I82.

Mounted on spacers I88 at an annular spacing inside shell I 88 is a quarter-wave combustion chamber or tubing I84 having open end I88 facing down stream, and head end I88 fltted with half-wave length air intake pipe I81 closedat its forward end but having air intake ports I88 mid-way of its length. For a description of such a half-wave length intake pipe see my aforesaid copending application Serial No. 128,766. Fuel is introduced to pipe I88 via fuel line I88, and may be metered by av suitably driven fuel pump, not

shown. Ignition, at least for starting, is provided by spark plug I18.

Assuming a forward velocity, air entering the open nose I82 flows rearwardly around the halfwave pipe I88 and the resonant tubing I84. and

i4 Owing to the expanding cross-section of the shell I88 from its nose I82 rearward, the velocity of the air flow within the expanding portion of the shell decreases and its pressure increases, as in a ram-jet," in accordance with Bernoulli's law. In this connection, it should be noted that the expansion of the shell should be sufficient to more than offset the fraction of the cross-sectional area occupied by the tubing I84 and its intake pipe I88, so that a super-atmosphere, or super atmospheric pressure, exists all around the tubing I84 and its intake pipe. It follows that the unit I84 will operate at an elevated mean pressure, which results, among other things, in a standing wave of increased Q, as discussed in my aforesaid application Serial No. 439.926.

Thus the air flow around air intake pipe I88 is at super-atmospheric pressure by the time it reaches intake ports I88. Air is deflected in through these ports by scoops or lips I88a, and thence flows 'to and through the resonant tubing I84. The operation of the tubing I84 is like that of the units already described, fuel from line I88 being intermittently exploded at combustion chamber region "I at the resonant frequency of the tubing I84. The length of tubing I84 is substantially a quarter-wave length measured in the hot gases traversing that tubing. The air intake pipe, closed at its forward end, is substantially a half-wave length measured in the cold air traversing it. The theory of such a half-wave air intake pipe is adequately set forth in my aforesaid copending application Serial No. 728.766; suffice it to say herein that the pipe I88 supplies air at substantially constant velocity to the combustion zone I1 I and that, in operation, not only are pressure and velocity anti-nodes P and V created respectively at the combustion zone "I and at the open end of the tubing I84, but a velocity antinode V appears in intake pipe I88 at intake ports I88, and a pressure anti-node P appears at the closed forward end of the intake pipe. Positive pressure peaks at zone "I compress the fuel charge, and ignition, by spark plug I18, or by flame lingering after the preceding explosion, causes an explosive gaseous expansion which operates as in earlier described embodiments. It will of course be understood that the ignition system (not shown) connected to the spark plug, and the fuel metering means are properly timed to the fundamental frequency of the tubing I84 in order to resonate the apparatus and create the standing wave. However, the system will automatically time itself when no ignition means other than lingering flame is utilized, and the fuel is fed at constant velocity. In such case, the standing wave created in the tubing I88 will automatically control the events of the cycle.

The shell I68 supplies air at super-atmospheric pressure to the open tail of the resonant tubing I84. with the several previously described beneflcial effects to the operation of the latter. The lowered velocity of the air flow around the tubing I84, as compared with air velocity outside the shell I88, results in an augmented secondary air supply to the velocity anti-node region V of tubing I84, which in turn means improvements in flame holding, mixing, completion of combustion, and rearward jetting from the tail of tubing I84. The latter effect, in turn, means additional pumping or propelling effect on the fluid flow through the shell, and hence increased velocity of jet discharge from the tail of shell I 88. Increase in jet discharge velocity results of course in increased finally discharges from the open rear end "I. 78 intake velocity at nose I82, and the overall effect 15 is augmented power of the entire apparatus. It is to be understood that the form of shell I60 is subject to modification; for example, it may be formed as a super-sonic difl'user, permitting super-sonic velocities.

With reference to the use of an acoustic burner in a ram-jet, it should be recognized that any conduit having definite discontinuities will necessarily have a resonant frequency pattern of its own. Therefore the conduit or shell I60 associated with the acoustic burner tube I64 will tend to become part of the resonant system because of mutual coupling. It is correspondingly advisable to select dimensions of the apparatus so that the acoustic burner and the conduit for the secondary air will be mutually cooperative and will not tend to spoil" or destroy resonance in the acoustic burner. Referring specifically to Fig. 11, I have found that there is a definite degree of acoustic coupling with the main air conduit IE at all openings in the acoustic burner I64. Therefore the relative dimensions of the two wave guides I60 and I64 should be such that the necessary impedance and phase relationships are maintained at these openings in the acoustic burner to allow its resonating with maximum amplitude. As an example, I find it advisable that the acoustic burner I64 be located in the main conduit I60 in a position that will not cause the discharge or low impedance end of member I64 to be at any region of high acoustic impedance which might exist in main conduit I60.

I claim:

1. A standing wave jet discharge heat engine which includes: a resonant housing defining and containing a fluid column in which may be established a sonic standing wave, having velocity and pressure anti-nodes, means for causing an intermittent combustion of fuel and air at the resonant frequency of said column at said pressure anti-node to create and maintain said standing wave. and a fluid duct arranged and directed to introduce air to said fluid column in the region of said velocity anti-node, said housing being provided with a wave expanding jet discharge fluid outlet leading from said velocity anti-node region of said fluid column.

2. A standing wave jet discharge heat engine which includes: a resonant housing defining and containing a column of fluid adapted to have a. standing wave established therein, said housing having therein pressure wave reflecting means located at one end of said column, and including pressure wave expanding means terminating the other end of said column, pressure disturbance means in pressure transmitting relationship with said fluid column operative at the resonant frequency of the fluid column, said reflecting means establishing a pressure anti-node of said standing wave adjacent said one end of said fluid column, and said wave expanding means establishing a velocity anti-node of said standing wave substantially nearer to said other end of said column than to said one end, a fluid duct arranged and directed to introduce fluid to said velocity anti-node region of said fluid column, and said housing having a jet discharge fluid outlet through which fluid is propelled by said standing wave.

3. A standing wave jet discharge heat engine which includes: a housing defining and containing a column of fluid adapted to have a standin wave established therein, said housing having therein pressure wave reflecting means at one end of said column, and having a fluid opening at the end remote from said wave-reflectin means through which fluid may be alternately -taken in and jet-expelled, pressure disturbance means in pressure transmitting relationship with said fluid column operative at the resonant frequency of the fluid column to establish a standing wave therein with a pressure anti-node thereof adjacent said reflecting means, and with a velocity anti-node nearer to said end of said column that is remote from said wave reflectin means, said standing wave operating alternately to take fluid into and expel fluid from said fluid opening, and a fluid duct arranged and directed to introduce fluid to the velocity anti-node region of said fluid column.

4. The subject matter of claim 3, wherein said fluid duct comprises a fluid conduit surrounding said housing and supplying fluid for intermittent aspiration into said housing through said fluid opening.

5. The subject matter of claim 3, wherein said fluid duct comprises a pipe opening into said housing in the velocity anti-node region thereof.

6. The subject matter of claim 3, wherein said fluid duct comprises a valve-controlled pipe opening into said housing in the velocity anti-node region thereof.

7. The subject matter of claim 3, wherein said fluid duct comprises a fluid flow conveying means for directing fluid to a region in immediate proximit to said fluid opening whereby said fluid can be aspirated into the housing by way of said opening.

8. A standing wave jet discharge heat engine, which includes: a resonant housing defining and containing a column of fluid adapted to have a standing wave established therein, said housing having therein pressure wave reflecting means at one end of said column establishing a pressure anti-node Of said standing wave thereadjacent, and having a fluid opening at the other end thereof for intake and jet discharge of fluid, said opening establishing a velocity anti-node of said standing wave thereadjacent, fuel combustion means operative at the resonant frequency of said fluid column arranged to supply expanding products of combustion at the region of said pressure anti-node and thereby create intermittent standing-wave-sustaining pressure pulses at said region, and an air duct for conveying auxiliary air to the region of said velocity anti-node in said fluid column.

9. The subject matter of claim 8, wherein said air duct comprises a conduit surrounding and spaced from said housing and carrying airflow between it and the housing which is available for intermittent aspiration into said housing through said fluid opening in said housing.

10. The subject matter of claim 8, wherein said air duct comprises a conduit surrounding and spaced from said housing and carrying airflow between it and the housing which is available for intermittent aspiration into said housing through said fluid opening in said housing, said conduit also serving to convey away airflow not thus drawn into the housing, as well as products of combustion discharged from said housing by way of its said fluid opening.

11. The subject matter of claim 8, wherein said air duct comprises a pipe opening into said housing in the vicinity of the velocity anti-node region thereof.

12. The subject matter of claim 8, wherein said air duct comprises a pipe adapted to be supplied with air under pressure and arranged to discharge 7 a 17 in the vicinity of the velocity anti-node region of said housing.

13. The subject matter of claim 8, wherein said air duct comprises a pipe adapted to be supplied with air under pressure and arranged to discharge in the immediate vicinity of said fluid opening" in said housing.

14. A standing wave jet discharge heat engine, which includes: a tubular resonant housing having a closed end and"*a'n-open end, said housing being adapted to contain a fluid column in which a standing wave can be sustained, with a pressure anti-node adjacent said closed end and a velocity anti-node adjacent said open end, fuel combustion means operative at the resonant frequency of said fluid column arranged to discharge expanding products of combustion at the region of said pressure anti-node and thereby create intermittent standing-wave-sustaining pressure pulses at said region, an enlarged chamber on the open end of said tubular housing, a jet discharge fluid outlet opening leading from said chamber, and an air duct arranged to convey and direct auxiliary air to the velocity anti-node region of said hous- 15. A standing wave jet discharge heat engine, which includes: a tubular resonant housing having a closed end and an open end for jet discharge of fluid, said housing being, adapted to contain a fluid column in which a standing wave can be sustained with a pressure anti-node adjacent said closed end and a velocity anti-node adjacent said open end, fuel combustion means operative at the resonant frequency of said fluid column arranged to discharge expanding products of combustion at the region of said pressure anti-node and thereby create intermittent standing-wave-sustaining pressure pulses at said region, and means associated with the open end of said housing for directing outside air radially inward into the region immediately to the rear of said open end of said housing.

16. In a compressor-turbine combination, the combination of: an air duct connected-between the discharge of the compressor and the intake of the turbine of said combination, a resonant burner housing spaced inside said air duct, containing a fluid column which extends in the direction of the air duct, said housing having a sound wave reflector at the upstream end of said column and an open end at the downstream end thereof, all in such manner that a standing wave may be created in said fluid column, with a pressure anti-node in the region of the reflector, and a velocity antinode in the region of said open end and fuel combustion means operative at the resonant frequency of said fluid column arranged to supply expanding products of combustion within said burner housing at the region of said pressure anti-node and thereby create intermittent standing-wave sustaining pressure pulses at said region, said air duct supplying auxiliary air to the velocity anti-node region adjacent said open end of said burner housing.

17. A jet propulsion apparatus which includes: a ram-jet housing having an air intake opening in its nose and a gas dispharge opening at its tail, said housing forming a fluid duct between said openings, a resonant burner housing spaced inside said housing, so as to permit fluid flow past the discharge end at said burner, said housing containing a fluid column which extends in the direction of said fluid duct, and having a sound wave reflector at the upstream end of said column and an open end at the downstream end thereof, all in such manner that a standing wave may be created in said fluid column, with a pressure antinode in the region of said reflector, and a velocity frequency of said fluid column arranged to supply expanding products of combustion within said burner housing at the region of said pressure anti-node and thereby create intermittent standing-wave-sustaining pressure pulses at said region, said fluid duct supplying auxiliary air to the velocity anti-node region adjacent said open end of said burner housing.

ALBERT G. BODINE, JR.

REFERENCES CITED The following references are of record in the file of this patent:

FOREIGN PATENTS Number Country Date 1,652 Great Britain Jan. 22, 1906 188,642 Great Britain Nov. 29, 1923 

